A surface plasmon resonance sensing device that is portable, and having the fiber sensing unit whose resonant wavelength being within the transmission range of a single-mode fiber or a multi-mode fiber, is disclosed. The disclosed sensing device comprises: a light source unit, a fiber sensing unit, an optical sensor, a plurality of fibers, and a computing and displaying unit. The fiber sensing unit includes a trench, a cladding layer, a core layer, a first metallic layer, and a plurality of dielectric thin film layers, wherein the first metallic layer covers the trench, and the plurality of dielectric thin film layers forms on the first metallic layer. The light source provided by the light source unit will become a light signal, after the light passes through the fiber sensing unit. The optical sensor transforms the light signal into a corresponding electric signal, for the usage of the computing and displaying unit.